Unlike non-rechargeable batteries, rechargeable batteries can be repeatedly charged and discharged. Lower power batteries in which battery cells are made into a battery pack are used as the power source for various portable electronic devices such as cellular phones, laptop computers, and camcorders. Larger battery packs which are formed by connecting several to tens of the rechargeable battery cells may be suitable for motor driven devices such as hybrid electric vehicles.
Rechargeable batteries may be classified into different categories based on external shape, for example, cylindrical and prismatic shapes.
Such a rechargeable battery is assembled in series by connecting rechargeable batteries together to form a rechargeable battery module to be used for driving a motor of an electric vehicle that requires a large electrical power capacity.
The rechargeable battery module is typically composed of a plurality of rechargeable batteries (hereinafter, referred to as “unit cells” for convenience) connected in series.
Because a rechargeable battery module is constructed by interconnecting multiple unit cells, the heat generated at the respective unit cells needs to be dissipated well. Particularly when a battery module is used to drive a motor for a hybrid electric vehicle (HEV), it is important to have adequate heat dissipation. If heat is not dissipated properly, the heat generated from the unit cells causes a temperature variation among the unit cells. The heat generated at the unit cells may also cause the temperature inside the unit cells to increase, resulting in explosion thereof.
Particularly, since a battery module for an HEV is charged and discharged by a high current, it may have deteriorated performance due to the heat generated by the internal reaction of a rechargeable battery.